Ballistic resistant articles which contain high strength fibers for use as structural members and panels for a wide variety of military equipment are known. Thus far one of the more successful fibers is a polyaramide and more specifically poly (phenylenediamine terephthalamide). Such fibers, in fabric form, are in their usual method of use encapsulated or embedded in a composite article of a thermoset resin.
In order for a composite to have its broadest application for a wide variety of ballistic resistant applications, it is important that it likewise possess a wide balance of important properties. Such uses range from structural armor to spall suppression liners. The properties include, of course, proper ballistic performance, that is, the composite functions satisfactorily as a ballistic armor system. Other required qualities are that the material be stiff and self-supporting, machineable, able to be formed into thick durable sections, fire-resistant, smoke-resistant, non-toxic, non-conductive and thermally insulative. One important property is that the composite be capable of being easily cut, trimmed, and drilled with if need be carbide or diamond tips. Composites with this needed balance of properties are not easily manufactured or widely available.
Military specification MIL-L-62474B provides a laminate, or composite, employing a polyaramide and a laminating resin which apparently is the cured reaction product of a polyvinyl butyral, phenol formaldehyde, trimethylol phenol, and phthalic anhydride. Such laminates have utility for armor applications and spall liners but one of their more notable deficiencies is that they are not easily machined and can be easily damaged (scratched etc.). Such laminates, for a given weight per square foot, generally are quite thick, and bulky, and yet are highly susceptible to buckling and high deformations. These characteristics lead to a waste of highly valuable space in military applications.
Thus it will be seen that there is a need in the art for providing composites with a balance of properties to make them useful for a wide variety of structural armor applications and spall liners and which are made of materials other than a polyaramide. There is also a need to provide for ballistic resistant composite materials which can be more easily machined and which have good water and weather resistant properties. It will also be apparent that there is a need for composites which on a weight basis have increased ballistic performance characteristics; that is there is a need for materials have increased ballistic performance (V.sub.50 PBL) at a given areal density. Such type materials with these many needed properties are reliably made in accordance with this invention and which for a given weight per unit of area are not bulky and have good resistance to buckling and deformation.